Mini-cold plate portable cooler

ABSTRACT

A thermal energy transfer device consisting of a closed container, a coolant hermetically sealed within said container, the container having a small portion which is relatively highly thermally conductive and a second substantially larger portion which has a relatively low thermal conductivity; and a thermally conductive member thermally connected to the small portion extending into the coolant.

United States Patent 1191 All ng r 1 1 Sept. 11. 1973 [54] MINI-COLD PLATE PORTABLE COOLER 2,876,634 3 1959 Zimmerman er al. 62/457 3,302,428 2/1967 Stoner et al. 62 371 [76] Arlen 2,494,719 1 1950 Rabjunn 165/136 St., Alameda, Calif. 94501 22 i Feb 7, 1972 Primary ExaminerCharles Sukalo Appl. No.: 224,168

US. Cl 165/47, 165/72, 62/371, 62/457 Int, Cl. F24h 3/00 Field of Search 62/457, 37l, 372; 165/47, 185, 186,80, 104, 135, 136, 72, 73

References Cited UNITED STATES PATENTS 10/1956 Picascia 62/457 Attorney-James R. Cypher 57] ABSTRACT A thermal energy transfer device consisting of a closed container, a coolant hermetically sealed within said container, the container having a small portion which is relatively highly thermally conductive and a second substantially larger portion which has a relatively low thermal conductivity, and a thermally conductive member thermally connected to the small portion extending into the coolant.

10 Claims, 3 Drawing Figures Pmmin mmn' SHEET 10F 2 FIG.I

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1 MINI-COLD PLATE PORTABLE COOLER BACKGROUND OF THE INVENTION This invention relates to portable, self-contained and reusable cooling units which employ a permanent, hermetically sealed quantity of coolant such as water or other non-toxic aqueous solution which may be frozen by separate, standard refrigeration methods. Such coolers are normally used for maintaining a chilled temperature in coffee creamers, for keeping beverages chilled or for medical purposes in keeping serums at a cool temperature.

SUMMARY OF THE INVENTION The gist of the present invention is the use of a device which steadily conducts thermal energy from a surface in contact with the body being maintained at a chilled temperature to the coolant of the device for a long period of time.

An object of the present invention is to provide an inexpensive, easily maintained device which has an extraordinarily efficient heat transfer capability for transferring the heat gain inthe substance being cooled to the body of coolant material.

Another object is to provide a device which has the ability to maintain the body being cooled at substantially the sametemperature for an unusually long period of time. i

A further object is to provide a device which can be relatively easily modified to changenthe heat transfer capability for different conditions. v

Still another object is to provide a device which can be chilled fairly rapidly so that the coolant may be frozen for reuse within a short period of time.

A still further object is to provide a device which can be used in relatively warm environments without causing surface condensation on the supporting parts of the container thereby causing wet spots on tablecloths and tables. I

Anotherobject is to construct a device from a few rugged and relatively rigid materials with relatively rigid connections so that the device 'can withstand forces induced through employing vacuum techniques, to withstand loads induced by the freezing coolant expansion, to withstand loads induced by handling,'andto provide firm support to the articles placed upon it.

A further object is to provide a device which may be.

maintained in a sanitary condition by cleaning in a standard dishwasher'and the coolant is non-toxic so that it will not contaminate food in the event of failure and is constructed to accommodate-avariety of different articles to be maintained at a cooltemperature.

BRIEF DESCRIPTION OF THE DRAWINGS vice taken substantially along line 3--3 of FIG. 1.

BRIEF DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention is a thermal energy transferdevice which consists briefly of a closed container 2, a coolant 3 hermetically sealed within said container, the container including a relatively small first portion or platform 4 having a substantially greater thermal conductivity than the remaining second wall portion 6 of the container surface area, a member 7 having a thermal conductivity similar to the first portion thermally connected thereto and projecting therefrom into the container so as to be continually submerged in the coolant, and means 8 insulating the second wall portion to prevent rapid heat gain from the surrounding environment.

The second portion of the first container may be constructed from various materials such as a polycarbonate plastic manufactured by General Electric Company under the trademark LEXAN. This material has the necessary toughness within the temperature range to which the device is subjected. The device is frozen within a freezer at less than 32 F. and is cleaned in a dishwasher where the temperatures are about F. The first portion of the first container may be constructed from any highly thermally conductive material, usually metal, such as anodized aluminum, or in several instances, stainless steel would be adequate. As shown in FIG. 2, the first portion may be a flat disc which is adhered to an annular rim 9 on the first conta'iner. Several adhesives may be used which can meet the various requirements imposed in this specific application; however, silicone rubber adhesive sealants are particularly well suited. In order to provide a good seal,

the first container may be constructed with. an annular depressed groove 11 surrounding the annular shoulder engagement with the metal disc 4. As shown in FIG. 2,

the adhesive 13 surrounds the gasket. The first portion is also held to the second portion by placing the coolant under partial vacuum at substantially an equivalent pressure to the vapor pressure of the water coolant. The forces induced by the pressure differential working with the adhesive bonding hold the parts together. Thus the plastic container 2 and the metal disc 4 form a closed first container.

The coolant contained in, the first container may be any of various fluids which freeze at temperatures within the range of standard home and commercial freezers. Water is a preferred coolant since it is nontoxic and would not contaminate food in the event of a failure of the container. Other well known solutions which freeze to a solid may be used.

One of the unique features of the present invention is the provision of a member which is connected to the first portion and is submerged in the coolant. Preferably the member is of the same metal as the first portion. Actually the plate and the member could be cast as an integral unit but in most instances the unit may be more inexpensively made by forming the members separately and joining them by various means suchas spot welding or by joining them with a very thin epoxy bond.

The means for insulating the first container may be of various forms ranging from a relatively thick walled plastic material having low conductivity to coatings of insulation applied to the walls of the first container. Preferably, the insulating means consists of a second container enclosing the second portion of the first container so that an air space is created between the walls.

and the upright walls 18 and 19 of the second container and the bottom wall 21 of the first container and the bottom wall 22 of the second container.

In order to reduce the heat transfer by convection and conduction, and to prevent excessive buildup of pressure when the device is washed in a hot dishwasher, the air may be evacuated between the walls of the first and second container to a reasonable vacuum. The two containers are joined at the top edge 23 of the second container and the lip 24 of the first container by an adhesive such as a silicon rubber adhesive sealant.

Another feature of the present invention is the configuration of the top surface of the first container. As shown in the drawings, a member or wall 26 surrounds the first portion of the first container in watertight relation and projects upwardly therefrom forming a dam for condensed water and air thermally cooler than ambient air. By trapping the condensed water, not only is the wetting of tablecloths avoided but, there is a functional use for the dam in trapping the cold air and holding it in close proximity to the body being cooled thereby extending the time period in which the device will maintain its ability to cool. Another unexpected result of providing the dam is the fact that when some water has collected on the surface 27 of the first portion of the first container, the water fills the air voids between the undersurface of the container being.

cooled such as the coffee creamer 28 and the surface 27. Thus the transfer of heat energy by conduction is improved. This dam may be formed in the first container by casting methods as shown in the drawings, or it may be a separate and independent part. As shown in the drawings, the walls of the dam slope inwardly towardthe center of the device so as to assist in centering an object such as a creamer.

The first and second containers may be constructed from opaque, translucent or clear materials depending upon the use of the devices. Translucent or clear materials give theadditional advantage of being able to visually determine when the ice has melted and needs to be frozen again or in determining when the coolant has been completely frozen and is ready for reuse. Coating the walls of the first container with a reflective coating will further extend the life of the coolant by decreasing the heat gain by radiation.

A further advantage of the present invention is the ability to select different size components so as to adjust the rate' at which heat energy is exchanged between the coolant and the object being cooled and the time period during which the device will be effective. Primarily, this is accomplished by selecting the size and number of members which project into the coolant. As shown in the drawings, two projections or fins 7 and 29 are shown. These fins may be attached separately to the disc 4 or they may be formed as one piece having a cross member 31 therebetween. By increasing any of the following, singly or jointly, the rate of heat exchange will be increased: the area of the fin in contact with the disc 4, the cross-sectional conduction area of the fin, the material thermal conductivity of the fin and the disc 4, or the number of fins. Conversely, the rate of heat exchange will be decreased by decreasing'any of the above stated control parameters either singly or jointly.

The device set forth may be used to cool a number of different things such as pitchers of cream which must remain cool on tables in heated restaurants for several hours during meal hours to maintain the fresh flavor of the cream and to inhibit bacteria growth. The device can be used at each individual place at the table to keep drinks cool and prevent excessive melting of ice cubes in the drinks. The efficiency of the device, however, is most fully realized in the applications where the item being cooled has a metallic container, the base of which has good thermal contact with the disc 4.

Tests have shown that a device constructed in accordance with the present invention will keep a cup of water in a metal container, chilled initially to about 45 7 F., at a temperature below 60 for over 5 hours in a room maintained at F. After a minute or two of initial thermometer response, the data show a fairly steady rise in temperature so that after 2 hours, the temperature stabilizes at about 60 F. During the first 20 minutes, the temperature is below 49 F and for the first hour, the temperature is below 55 F. These test results were made with a unit in which the first container was approximately 2 1% inches in diameter and 2 9% inches in height. Different results may be obtained by varying the size of the coolant chamber, the amount of coolant, and the size and number of fins. The fin used was approximately 1 1% inches long, one-half inch in width, and approximately one-sixteenth inch in thickness. In the device set forth above, the coolant chamber had a volume of 149 cubic centimeters (cc.) and the volume of the coolant which was water was cc.

The unique ability'of the present invention to exchange thermal energy with another body at such an even rate and for such a prolonged period of time is perhaps due to several factors which acting in concert lead to this unusual result. First, if'the device is inverted, the coolant will freeze in touching contact with the metal disc 4. Thus when the device is placed on the table, there is a direct heat exchange by conduction between the disc4 and the frozen coolant. Further, due to the presence of the fin 7, instead of the ice melting .and dropping to the bottom of container 6, the ice tends to stick to the fin and hold the ice close to the plate 4 where the ice is still in close proximity to the plate 4 even though the ice melts directly beneath the plate 4. Thus some heat exchange between the plate 4 and the ice is carried on by the process of radiation. There is a freezing and refreezing process taking place at the lower end of the fin 7 because the ice tends to cling to the fin for an amazingly long time even after a substantial portion of the ice has melted. Thus heat energy transfer continues to take place by conduction between the ice and the fin for a long period of time. This heat energy transfer travels by conduction from the fin to the plate 4 and thence to the container, such as container 28. This transfer is rapid and therefore enables the cooler to rapidly compensate for rapid buildups in heat in the container such as when the cream-pitcher is picked up in a warm hand, and held momentarily over a hot cup of coffee before being returned to the device.

An unexpected result observed from the utilization of a depending fin 7 is the fact that the ice is always in touching contact with the fin for as long as there is any substantial amount of ice. This is most desirable since the heat transfer between ice and metal is always greater than betweenthe ice and water. It has been observed that the ice melts in the vicinity of the fin, but since the ice floats, and since the ice does not melt uniformly, the ice block is always somewhat askew and tends to touch the fin at one or more points.

One other means of transferring heat energy is efficiently utilized by the device, and that is by radiation. As long as the ice block is in contact with or in close proximity to the bottom side of the disc 4, the warmer metal disc radiates heat to the ice. Even after the ice drops down and beings to float, the fin remains in very close proximity or in direct contact with the ice and again, the Wanner fin radiates heat directly to the ice.

in summary, this device conducts heat rather evenly and very efficiently from the body being chilled to the coolant, and at the same time is thermally insulated on all sides except where it is designed to conduct thermal energy, so that the coolant may last as long as possible and function without wasting its cooling capability through receiving unwanted ambient heat energy.

Iclaim:

1. A thermal energy transfer control device compris-' a. a first container having a base and upturned side walls formed from thermally insulating material;

b. a freezable liquid coolant filling a portion of said first container;

c. a relatively small platform member attached to the upper portion of said side walls and forming a hermetical seal therewith and constructed from a material having a substantially greater thermal conductivity than said base and side walls of said first container;

d. said side walls and. platform member forming a thermally insulating air chamber between the upper surface of said coolant and said platform member; e. a thermal control member having a thermal conductivity similar to said, platform member connected thereto in good thermally conductive contact and projecting therefrom downwardly through said air chamber into said first container so as to be continually submerged in said coolant when in a liquid state and in contact with said coolant, when in a solid state;

f. means insulating said base and side walls of said first container to prevent rapid heat gain from the surrounding environment;

g. said air chamber insulating said coolant from said platform so that the primary portion of the heat flow "between said platform and coolant is transferred by said thermal control member; and

h. said thermal control member having a size selected upon the basis of the rate of heat conductivity de sired to be conducted from said platform to said coolant and requiring noxchange in the size of said first container or said platform or the amount of said coolant. j j

2. thermaltransfer control device as described in claim 1 comprising: i Y

a. said means comprising a second container enclosing the'base and side walls of said first container and providing an air space therebetween.

3. A thermal transfer device as described in claim 2 comprising:

a. the space between said first and second containers being hermetically sealed and under a vacuum.

4. A thermal transfer device as described in claim 1 comprising:

a. said coolant being primarily water and the volume of said water while in a liquid state being limited with respect to the volume of said container partly to permit expansion of said coolant upon freezing; and

b. said water coolant being sealed under partial vacuum at substantially an equivalent pressure to the vapor pressure of the said water coolant to maintain reasonably low pressures upon heating to anticipated temperatures encountered in standard, automatic dishwashers by virtue of the inherent vapor pressure properties of the said water coolant in conjunction with the exclusion of additive pressure effects of air within said coolant container.

5. A thermal transfer device as described in claim 1 comprising:

a. a member surrounding said platform in watertight relation and projecting upwardly and outwardly therefrom forming a dam for condensed water and air thermally cooler than ambient air.

6. A thermal transfer device as described in claim 1 comprising:

a. said platform being constructed from metal and said first container being constructed from plastic; and a b. said air chamber providing communication between said first container and said platform so that when said device is turned .over said coolantfiows into contact with said platform for rapid freezing of said coolant. j l

7. A thermal transfer device as described in claim 6 comprising: v

a. said platform having a substantially smooth surface positioned on a substantially horizontal plane when the thermal transfer device is in its normal, upright use orientation. j v v 8. A thermal transfer device as described in claim 6 comprising:

a. said side walls of said first container being constructed from a light transmitting material thereby permitting visual ascertainment of the state of the contents; and

b. said means consisting of a second container constructed from a light transmitting material, and the second container enclosing thebase' and side walls of said first'container and providing an air space therebetween. l

9. A thermal transfer device as described in claim 3 comprising: I

a. said means incorporating a reflective coating.

10. A thermal transfer device as described in claim 4 comprising:

a. said platform and the upturned side walls of said first container being constructed of separate individual members and being sealed and joined at their common interface in such a manner and by an I adhesive selected to permit seal breakage under temperatures higher than normal operating temperatures thereby preventing calamitous or catastrophic explosion of said container.

. a: i t =0: e 

1. A thermal energy transfer control device comprising: a. a first container having a base and upturned side walls formed from thermally insulating material; b. a freezable liquid coolant filling a portion of said first container; c. a relatively small platform member attached to the upper portion of said side walls and forming a hermetical seal therewith and constructed from a material having a substantially greater thermal conductivity than said base and side walls of said first container; d. said side walls and platform member forming a thermally insulating air chamber between the upper surface of said coolant and said platform member; e. a thermal control member having a thermal conductivity similar to said platform member connected thereto in good thermally conductive contact and projecting therefrom downwardly through said air chamber into said first container so as to be continually submerged in said coolant when in a liquid state and in contact with said coolant, when in a solid state; f. means insulating said base and side walls of said first container to prevent rapid heat gain from the surrounding environment; g. said air chamber insulating said coolant from said platform so that the primary portion of the heat flow between said platform and coolant is transferred by said thermal control member; and h. said thermal control member having a size selected upon the basis of the rate of heat conductivity desired to be conducted from said platform to said coolant and requiring no change in the size of said first container or said platform or the amount of said coolant.
 2. A thermal transfer control device as described in claim 1 comprising: a. said means comprising a second container enclosing the base and side walls of said first container and providing an air space therebetween.
 3. A thermal transfer device as described in claim 2 comprising: a. the space between said first and second containers being hermetically sealed and under a vacuum.
 4. A thermal transfer device as described in claim 1 comprising: a. said coolant being primarily water and the volume of said water while in a liquid state being limited with respect to the volume of said container partly to permit expansion of said coolant upon freezing; and b. said water coolant being sealed under partial vacuum at substantially an equivalent pressure to the vapor pressure of the said water coolant to maintain reasonably low pressures upon heating to anticipated temperatures encountered in standard, automatic dishwashers by virtue of the inherent vapor pressure properties of the said water coolant in conjunction with the exclusion of additive pressure effects of air within said coolant container.
 5. A thermal transfer device as described in claim 1 comprising: a. a member surrounding said platform in watertight relation and projecting upwardly and outwardly therefrom forming a dam for condensed water and air thermally cooler than ambient air.
 6. A thermal transfer device as described in claim 1 comprising: a. said platform being constructed from metal and said first container being constructed from plastic; and b. said air chamber providing communication between said first container and said platform so that when said device is turned over said coolant flows into contact with said platform for rapid freezing of said coolant.
 7. A thermal transfer device as described in claim 6 comprising: a. said platform having a substantially smooth surface positioned on a substantially horizontal plane when the thermal transfer device is in its normal, upright use orientation.
 8. A thermal transfer device as described in claim 6 comprising: a. said side walls of said first container being constructed from a light transmitting material thereby permitting visual ascertainment of the state of the contents; and b. said means consisting of a second container constructed from a light transmitting material, and the second container enclosing the base and side walls of said first container and providing an air space therebetween.
 9. A thermal transfer device as described in claim 3 comprising: a. said means incorporating a reflective coating.
 10. A thermal transfer device as described in claim 4 comprising: a. said platform and the uptUrned side walls of said first container being constructed of separate individual members and being sealed and joined at their common interface in such a manner and by an adhesive selected to permit seal breakage under temperatures higher than normal operating temperatures thereby preventing calamitous or catastrophic explosion of said container. 